Personal views on the selection of general centrifugal pumps

Pump selection principles 1. Make the type and performance of the selected pump meet the requirements of process parameters such as device flow, head, pressure, temperature, cavitation flow, and suction lift. 2. Mechanical aspects include high reliability, low noise and low vibration. 3. Economically, the total cost of equipment, operation, maintenance and management fees should be taken into consideration to minimize the total cost. 4. The centrifugal pump has the characteristics of high speed, small size, light weight, high efficiency, large flow rate, simple structure, pulsation-free infusion, stable performance, easy operation and convenient maintenance. Therefore, except for the following situations, centrifugal pumps should be used as much as possible: When there are metering requirements, the metering pump has a high lift requirement, the flow is very small and there is no suitable small flow high lift centrifugal pump to choose from, a reciprocating pump can be used. If the cavitation requirements are not high, a vortex pump can also be used. When the head is very low and the flow rate is large, axial flow pumps and mixed flow pumps can be used. When the viscosity of the medium is large (greater than 650~1000mm2/s), you can consider using a rotor pump or a reciprocating pump (gear pump, screw pump). The gas content of the medium is 75%, the flow rate is small, and the viscosity is less than 37. At 4mm2/s, a vortex pump can be used. For occasions where startup is frequent or pump filling is inconvenient, pumps with self-priming performance should be selected, such as self-priming centrifugal pumps, self-priming vortex pumps, and pneumatic (electric) diaphragm pumps. final note: When selecting a pump, you must fully consider the displacement, head, power, liquid medium, temperature, etc. of the water pump per unit time.

The lecture above is very comprehensive. I feel that apart from equipment fees, operation fees, maintenance fees and management fees, which need to be considered by the user, other technical issues such as pump selection are best left to the pump manufacturer. As long as the technical parameters and working conditions are complete, the pump manufacturer will give you the best advice, and the customer can only make the final decision.

Generally, centrifugal pumps mainly choose manufacturers, which involves pump quality, operating efficiency, operation and maintenance volume, etc. Because it is a serialized product, you don’t need to think too much about other aspects.

The first floor is about practicality, and the second floor is about theory. Especially the low speed one. I once had an underground pool with hot water that was around 45 degrees Celsius. The pump I used at the beginning was equipped with a 2-pole motor, and the flow rate and head were about the same. It was repaired almost several times a week, and the shaft seal and gasket broke all day long. ； Later, I got angry and increased the flow rate and head. After the pump arrived, I changed the motor to a 6-pole one and the pool to an above-ground one. Haha, I haven’t done much repairs for half a year! It just took a little effort when I started replacing the motor.

Don’t you know that API requires pumps to operate continuously for three years? I would like to ask you, if a pump often breaks down and the manufacturer comes to repair it frequently, is it better to keep working normally? If it is a product pump and it breaks down frequently, how can you ensure the quality of the product you install? And the second point you mentioned is that the efficiency of low-speed pumps is obviously lower than that of high-speed pumps. You said that the seals are more durable at low speeds. I disagree with this point. Common mechanical seals are contact liquid film seals. If the speed is lower than a certain level, a stable liquid film cannot be formed and the sealing surface will wear. Is this beneficial to mechanical seals?

I know what you said makes sense, but* In fact, leakage of pumps is unavoidable in the factory. They run continuously 24 hours a day. However, the actual situation is that high-speed pumps do have certain problems. The efficiency must be higher. If you increase the power of the impeller motor, the power of the impeller motor must be larger. However, judging from the reflections and subsequent processing of many manufacturers, they have replaced large impellers and six-stage motors, especially pumps for crystallized materials. Among them, the motor of high-speed pumps Mechanical seals are indeed prone to leakage. Under the same process conditions, the usage time differs by about 3 times. In addition, the high-speed coupling part is also relatively easy to damage, such as the connection part of the rigid coupling. If it is not tight, it will cause serious collision and rotation over time. The use time of the pad is not long. In theory, there should be no problem. In fact, it is not very practical. It would be better if double-end faces are used instead.

I don’t know what product LZ should choose. If it is light oil, I can provide a submersible pump for LZ with a three-year warranty. The manufacturer guarantees trouble-free operation for three years. Within three years, if quality problems occur, the user will be replaced with a new pump. If LZ needs it, you can add me on QQ: 944840216. Or contact by mobile phone: 15522981361

There is a lot of information about this online, I hope you can learn more* study *

Speaking of centrifugal pumps, I think that after selecting the pump, it is also important to select the check valve in front of the pump. Do you have any user-supplied ones? Talking about the relationship between these two equipment selections will help equipment manufacturers tailor their products. We look forward to the healthy development of our equipment industry!

When selecting a pump, I think you should first look at the flow rate, otherwise the power loss may be inappropriate. Then choose the pump model. The main reason is to look at the flow rate and lift. The power loss must be calculated, otherwise it will be more troublesome and may cause the material to be transported too slowly.